Battery-Free Mobile Devices Communicate Pulling Signals From Air

Researchers at the University of Washington (UW) have developed wireless devices that are powered and communicate solely by harvesting signals from existing television and cellular transmissions in the air.

The enabling technology, called ambient backscatter, transforms existing wireless signals into both power source and way to communicate, according to researchers from the university’s computer science and engineering department. They posted a video demonstrating how the technology works on the university’s website.

The research, which was partially funded by the National Science Foundation, was led by Shyam Gollakota, a UW assistant professor of computer science and engineering. Fellow professors Joshua R. Smith and David Wetherall, as well as students Vincent Liu, Aaron Parks, and Vamsi Talla co-developed the technology.

Researchers at the University of Washington have developed wireless devices that are powered and communicate solely by harvesting energy from existing television and cellular transmissions. The technology is called “ambient backscatter,” and it transforms existing wireless signals into both power source and way to communicate. (Source: University of Washington)

Ambient backscatter has the potential to provide power and communication to a wide range of devices and items as part of the Internet of things, as well as smart-city and smart-home technology, researchers said in the video. They explain how one day the technology could be integrated into keys, walls, couches, or any number of items to provide communication capabilities.

Initially, however, mobile devices are the target for the technology, providing power and communication capabilities to a ubiquitous device that’s still dependent on a battery charge to remain functional, Liu told Design News.

“We think this technology has the ability to open up more applications than you or I could ever dream up,” he said. “I think one would be to significantly reduce the power consumption of our cell phones while idle. We might even be able to make phones that, with minimal use, could last for weeks, months, or even longer.”

Modern mobile devices could be easily fitted to utilize the technology by reusing antennas already available in these devices and adding a “relatively simple circuit,” Liu said. The technology works through sensors that either absorb or reflect radio waves from TV towers and other transmissions in order to send and receive messages. The devices do not emit RF signals themselves, and so do not need a transmitter like typical RFID technology does.

The technology sounds slightly similar to an energy harvester developed by a German university student that also picks up on transmissions from mobile devices, electricity towers, and the like, and stores it to provide energy to power devices. However, that device does not allow for communication; it merely provides power.

The ambient backscatter-powered devices developed by the UW team, on the other hand, actually need to use signals that both communicate and power the device in order to work successfully, Liu told us. “For these types of devices, communication is an essential part of their operation, and thus powering the device necessitates the ability to power communication,” he said. “It turns out that the amount of power you can harvest from ambient signals isn't enough for traditional communication. Ambient backscatter is orders of magnitude lower power than traditional communication, and thus, because our system enables ultra-low-power communication, it enables us to power the device.”

Researchers plan to continue to develop the technology to increase the distance over which the devices can communicate. They will try to make the technology viable for use with any ambient radio source, as well as add other enhancements, Liu said. There is no timeline yet for commercialization.

"Researchers at the University of Washington (UW) have developed wireless devices that are powered and communicate solely by harvesting signals from existing television and cellular transmissions in the air."

Elizabath, that's great and I think self powered board is a good model. I would like to whether anywhere (cell/battery) the energy is stored in wireless device or it's like a real time sourcing from air.

I agree. This technology could really help with in-the-field devices that are placed in places where batteries are hard to change. This also sounds like the ambient power sources is easier to harvest than ambient vibrations. Not all device placements are near freeways and bridges.

He said he thinks the technology could open up more applications than you could ever dream of. I second that notion. This is very futuristic. Considering how much stray RF there is floating in the air, right in front of your eyes, at this very instant; I always thought it was a fascinating fact that turning on a transistor radio right in your hand could catch the signal of anything transmitting within 50 miles. Think of how much energy that actually is, available for this harvesting concept!

Fair point, jhankwitz, I suppose the potential to use this energy has been around for a long time and, as you point out, people have already been doing it. But I think now it will be utilized more on a larger scale.

Jhankwitz- My hat's OFF to you, and with great admiration, recognize that you had the foresight to understand and prototype this RF phenomenon over 60 years ago. Kudos --

I say futuristic because this idea, if it were broadly developed and commercialized, would rock the paradigm of powering wireless communication devices. I realize the losses are a big issue, but the concept of wireless charging was just a dream only a few years ago and now is commercialized. With this, we skip the charging, and go straight to powering. Seems futuristic to me.

No foresight on my part. Every 7th grader learned how to use hand and power tools and built a table and chair, and every 8th grader fabricated an electric motor out of a coffee can in addition to a crystal radio. Everyone also had to learn how to play a musical instrument as well as dance. Back then, they prepped kids with a broad spectrum of activities to help them determine their interests and choose their futures.

Well, not "every" student. Those first two were what the boys got to do in wood and metal shop, at least in my school. Girls learned cooking and sewing. I'm glad I learned both, but I also wanted to learn all that stuff in shop, too. Not only did this help us--along with music and art for everyone--figure out what we wanted to do, it also gave us some excellent skills. And there was also PE, which helped keep us all healthy.

You're so right Ann. Back in the early '50s, just about the only acceptable jobs for women were teacher, secretary, or housewife/homemaker. It was a whole different culture. The temporary "Rosie the Riveter" was no longer needed and had returned to homemaker status.

jhankwitz, those restrictions continued into the 60s and 70s, which is what all the screaming (and Title IX, among other things) was about. I still wish I'd been "allowed" to take architectural drawing along with the boys in high school. Good thing science and math weren't off-limits! And thanks for the Rosie the Riveter reminder. I guess we were supposed to forget that women had been doing all that stuff already.

You are lucky, Ann--I didn't get to learn any of that stuff in school (neither cooking nor sewing...nor shop-like things like working with tools) and had to learn much of it in the school of life, so to speak. There are definitely things I wish someone had taught me when I was young and more sponge-like. The adult mind doesn't absorb things as fast or easily. Of course, the experience of discovering and learning new things over the years has definitely been rewarding.

Elizabeth, I agree--at some point, schools started eliminating anything useful or practical, or fun: art, music, P.E., sewing/cooking or wood/metal shop. Regarding continuing education, I've been a lifelong learner. In high school I basically taught myself how to use simple carpentry tools. Now there's a ton of free how-to videos on YouTube to learn just about anything you can imagine. So in some ways there's a lot more than before. But I agree--it's best to start with some things earlier in life.

Yes, Ann, I have to say...now that I am approaching middle age I realize the most useful things I have learned in my life I did not learn in school. But it's also good because it means I still get to learn new things all the time, which keeps life fun and interesting. :)

I meant to comment on this earlier and forgot. Yes, this is totally true especially in one case (something I struggle with all the time living in a foreign country): language. I am still not a fluent Portuguese speaker (I get by, but it's not great) after nearly four years in this country, yet I watch chlidren with parents from different countries chatter away in each of their parents' languages and English, too (if it's not one of their parents' first languages). Kids really are sponges! Shame our brains turn to mush for these sort of things as we age.

Although studies show that nearly everyone is a linguistic sponge for the first few years of life, some people acquire language more easily than others, and can continue to do so later on. I've noticed it runs in families; mine, for instance. I still remember some of the French I learned in high school and used when I was there in my 20s, and two other immediate family members were nearly bilingual in Spanish. For other people, learning hands-on stuff like auto repair or cooking, gardening, sewing or construction is easy to learn at any time in life.

Yeah, I was a 'shop' student in the 70's, too. Wood Shop, metal shop, auto-shop, drafting, both machine and architectural. 'Shop-Class' directed me to a career in Engineering. (Acknowledgement to Ann, also, that girls took Home-Economics. Quite sexist, in retrospect, wasn't it?) But the realization that stray RF was a potential power source was not part of the curriculum, and I think it was (and is) an overlooked and misunderstood phenomenon. I think you minimize your early realization of it. You were a smart kid, jhankwitz.

Indeed, JimT, while this capability has been around for a long time, the ability to get it out there to the masses would be game-changing indeed. Perhaps we're not far off, given the amount of research going into this space at the moment.

It definitely seems like a good solution for these types of situations, Rob. I remember that I did a story about a similar device that harvests energy from ambient electricity sources developed by a German student, and there was a lot of debate about "stealing" the electricity. I didn't really agree with this theory, but I'm wondering if anyone thinks so in this case, too. http://www.designnews.com/author.asp?section_id=1386&doc_id=260486

Elizabeth, I recall reading the article you wrote. I say we are not stealing if we just take a small amount of radio signal to power a small device. It would probably have gotten reflected and wasted anyway. Now if we were to put up a big antenna array or web to get power, that might rob users in line of sight from getting the signal from the tower.

Regarding electric power lines; if someone just charges a cell phone by capturing the magnetic field from a utility line, I doubt that anybody would notice or care. If 10,000 people did this near the same line, someone would care. I have heard of farmers who laid a half-mile long wire parallel to a power line crossing their property with the purpose of capturing the magnetic flux as AC current. That qualifies as stealing for sure because the magnetic field cannot return to the utility line.

I vaguely recall that a traffic signal in Israel is powered by road vibrations as cars pass over piezo devices. That is not stealing anything as nobody has a vested interest in road vibration.

Thanks for clarifying that and providing that perspective, 78RPM. Yes, it probably would be a big problem if regular electricity service or RF signals were interrupted, but I agree with your points and think these new energy harvesters are quite ingenius and a good way to leverage existing energy that otherwise would be wasted.

1. I remember the story of the Dairy Farmer stealing from the high voltage lines; an EE professor told that story in ~1980. Suggested he probably would still be doing it today, had he kept his harvest to a smaller trickle.

2. Different topic of power from road vibrations; An article was right here in DesignNews, a few weeks back. See http://www.pavegen.com/ . Great idea - Waiting for their IPO, on the London exchange!

3. Last, on using Zigbee and sleep mode for extended battery life on wildlife tracking: I was on a team that developed such a device, but funding slumped and the product was never realized. Such is the success of engineering.

JimT, your dream in point number 3 might have been realized. Take a look at http://www.telemetrysolutions.com for their wildlife tracking solutions that include GPS tracking, tracking specific kinds of animal movement (feeding, nesting, moving), and capture of solar energy for battery life approaching the shelf life. They offer smart GPS which lets the device sleep in low power mode during times of inactivity, and remote download of data. There are other trackers from Lotek, Telonics, and Vectronic Aerospace but this one from telemetry solutions looked feature rich from the point of energy harvesting.

Laughing a little – Yah, I do know it was realized – Just not by OUR team. At the time (2007) we had a leg up, being ahead of the competition; but we collapsed financially, and the completion surged ahead.

"his technology could really help with in-the-field devices that are placed in places where batteries are hard to change. This also sounds like the ambient power sources is easier to harvest than ambient vibrations. Not all device placements are near freeways and bridges."

Rob, you mean that there are cells and its getting recharging by pulling signals from air.

MyDesign, for a few years now, we're seen devices produced that receive their energy from vibrations in the air do to traffic on freeways or traffic over bridges. While this technology allows devices to work without batteries, the device does need to be within range of vibration. The devices described in the article could be placed anywhere, since the power they grab from the air is everywhere.

A wildlife biologist contacted me to ask how he could extend the battery life of animals he was tracking. I told him there are tracking collars that can sleep 90 percent of the time using a micro-amp of current while storing sunlight energy during the day. These devices might only need to wake up to get some data for a second and transmit it to a Zigbee or wi-fi device or a satellite -- then go back to sleep.

Design News and Digi-Key sponsored a class by Paul Nickelsberg April 15 - 19, 2013 on energy harvesting. I was amazed that in lectures four and five, he introduced devices that could harvest energy that produced only millivolts of output (vibrations, for example, and signals from the "air"). What's cool is that these signals from microwave radiation would have been just wasted. In fact, they might have contributed to reflected confusion in other networks, so harvesting these might do others a favor. Well, not really. There is so much radiation out there.

I encourage others interested in this subject of harvesting micro amounts of energy to take the archived class.

Thanks for this perspective and that information, 78RPM. There really is a lot of potential in energy harvesting, especially for these micro devices. In fact, it's really probably the best application of the technology, given that a lot of them don't need a lot of power and could really be self-sustaining.

There was a project in an issue of Popular Electronics in 1958 called "Stolen Power Radio" and I built one and it worked well. It was 2 AM radios on a single board. the first was a standard 2 transistor AM radio and the second was just the tuner section and a diode rectifier. You would temperarily connect a headphone th the second radio and tune it to the strongest AM station in town and then the rectified signal would power the second radio.

As an experiment I extended the leads of my Fluke meter in opposuite directions with it set to AC volts. I see abot 5 volts developed across about 20Megohms. That is plenty enough field to make a bug hum in a microphone circuit, but there is not a lot of current available. The same experiment with my 50,000 ohms per volt multimeter shows no meter deflection. So while the potential is there the source impedance is in the tens of megohms. Since the avarage battery has much less than an ohm for internal resistance, it becomes clear that harvesting electrostatic fields will provide micro watts of power, not watts.

@ Mydesign, you have posed a relevant question because it is not mentioned in the article whether power is actually stored in the device's battery or it is just a live source of power and dies away as soon as the source is turned off. I would love if ambient power could be stored somehow.

Powering the device by using television and cellular transmissions in the air would be a revolutionary thing even without any communication capability. People are availing communication services provided by a number of companies. Dead battery is a problem many times especially for on field professionals. If there could be such power source, people won't bother if it gives them the ability of free communication or not.

This would certainly benefit Rainforest Connection with their cell phone monitoring project for illegal deforestation. Their using solar cells to power old cell phones that listen for the tell-tale sound of chainsaws cutting down trees.

It won't be too much longer and hardware design, as we used to know it, will be remembered alongside the slide rule and the Karnaugh map. You will need to move beyond those familiar bits and bytes into the new world of software centric design.

People who want to take advantage of solar energy in their homes no longer need to install a bolt-on solar-panel system atop their houses -- they can integrate solar-energy-harvesting shingles directing into an existing or new roof instead.

Kaspersky Labs indicated at its February meeting that cyber attacks are far more sophisticated than previous thought. It turns out even air-gapping (disconnecting computers from the Internet to protect against cyber intrusion) isn’t a foolproof way to avoid getting hacked. And Kaspersky implied the NSA is the smartest attacker.

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